#5.4
import turtle
def koch(size, n):
    if n == 0:
        turtle.fd(size)
    else:
        for angle in [0, 60, -120, 60]:
            turtle.left(angle)
            koch(size/3, n-1)
def main():
    turtle.setup(800,400)
    turtle.speed(0)  #控制绘制速度
    turtle.penup()
    turtle.goto(-300, -50)
    turtle.pendown()
    turtle.pensize(2)
    koch(100,2)     # 0阶科赫曲线长度，阶数
    turtle.hideturtle()
main()
